This invention relates to method and apparatus involving cartridges for use in flash chromatography and low pressure liquid chromatography equipment.
Chromatographic analysis passes fluids through columns containing specially treated sorbent which allows the chemicals in the fluid to be eluted at different times and thus form separated peaks on a chromatogram. In order to prepare or clean up the fluid being analyzed the fluid is often passed through a sorbent under pressure. Further, for low pressure liquid chromatography (LPLC) or flash chromatography the fluid may be passed through a sorbent at a pressure of 20-100 psi. This operating pressure is sufficiently high that these cartridges, which have relative large diameter bodies leak at the seams. Threaded connections are thus not used to form the body when the body is made of polymers. Thus, these cartridges are traditionally made of plastic and have sonically welded ends. But even that welded construction will leak if there are defects in the welds. That welded construction and the accompanying manufacturing and material costs cause in undesirably high costs, especially as the cartridges must be either discarded, or must under go extensive and thorough cleaning after a single use, or at most after a few uses with similar fluids. There is thus a need for a low cost, disposable cartridge.
Further, the welded construction requires the chromatographic packing material be placed in the cartridge before it is welded, or it requires careful packing of the column under pressure, both of which limit the usefulness of the cartridge and increase its cost.
Recently one company has introduced a disposable cartridge made of molded polypropylene having an end fitting that uses openings in a number of cantilever members to engage detent members which fit into the openings to create an interference fit to snap-lock the end fitting onto the cartridge. This is described in U.S. Pat. No. 6,565,745. But this interference fit is created at the factory and again creates a cartridge that does not allow the user to easily vary the contents of the cartridge. There is thus a need for a cartridge that allows a user to easily vary the contents.
Secondary cartridges are sometimes tied into the system for use, but these secondary cartridges are limited in size to 70 ml (or between 20-25 g of material). These secondary cartridges lie with tubing 1 to 2 feet away from the sample. The use of secondary cartridges increases the amount of run time and expensive solvent, due to elution of the sample. It causes dilution of sample because the cartridge is 1 to 2 feet away from the sample. The tubing and secondary cartridge also allows the addition of air which may or may not affect the chemical composition or performance. Also secondary cartridges have a capacity limit of 20-25 g which does need meet the needs of all users since at times up to 60 g is needed to be loaded. This forces an end user to separate the chemicals into several separate cartridges. The secondary cartridge is also an additional expense, and requires additional time for loading.
There is thus a need for a cartridge that can be sealed to function under LPLC pressures but which allows the user to access the inside of the cartridge before it is sealed.
Moreover, welded cartridges are limited by being pressure rated to only about 45 psi, due to leaking and instability at higher pressures. This pressure limits the end user, because high pressures are desirable for separating chemical compositions that are thick and viscous. Without these higher pressures these thick, viscous chemicals can not be distinguished. There is thus also a need for a larger capacity cartridge that can be used at higher pressures, especially for viscous fluids.
In LPLC the fluid sample is sometimes prepared by passing it through one or more cartridges of different material, each of which has a different sorbent to clean the fluid of particular undesirable materials or chemicals. Because the fluid sample can vary, a wide variety of cartridges with different sorbents sealed in the cartridges must be maintained. Further, the removal and reconnection of these various cartridges is cumbersome and time consuming, and the cost of each cartridge is expensive. There is thus a need for a way to reduce the complexity and cost of using different sorbents.
Sometimes a Y fitting is used to inject one or more fluids into the LPLC cartridge. The connection and use of these Y fittings is cumbersome. Further, the fitting must be either discarded or cleaned after each use. There is thus a need for a better and less expensive way to introduce fluid or materials into the cartridge.